1. Digestive System
A&P

2. Digestive System AKA gastrointestinal system or GI system
Function=responsible for the physical & chemical breakdown of food so it can be taken into bloodstream & be used by body cells & tissues
Structures=divided into alimentary canal & accessory organs

3. Alimentary Canal Long muscular tube Includes: Mouth Pharynx Esophagus
Stomach
Small intestine
Large intestine

6. 1. Mouth Mouth=buccal cavity
Where food enters body, is tasted, broken down physically by teeth, lubricated & partially digested by saliva, & swallowed
Teeth=structures that physically break down food by chewing & grinding in a process called mastication

7. 1. Mouth
Tongue=muscular organ, contains taste buds which allow for sweet, salty, sour, & bitter sensations
Tongue also aids in chewing & swallowing

8. 1. Mouth
Hard palate=bony structure, forms roof of mouth, separates mouth from nasal cavities
Soft palate=behind hard palate; separates mouth from nasopharynx
Uvula=cone-shaped muscular structure, hangs from middle of soft palate; prevents food from entering nasopharynx during swallowing

10. 1. Mouth
Salivary glands=3 pairs (parotid, sublingual, & submandibular); produce saliva
Saliva=liquid that lubricates mouth during speech & chewing, moistens food so it can be swallowed
Salivary amylase=saliva enzyme (substance that speeds up a chemical reaction) starts the chemical breakdown of carbohydrates (starches) into sugar

12. 2. Pharynx Bolus=chewed food mixed with saliva
Pharynx=throat; tube that carries air & food
Air goes to trachea; food goes to esophagus
When bolus is swallowed, epiglottis covers larynx which stops bolus from entering respiratory tract and makes it go into esophagus

14. 3. Esophagus Esophagus=muscular tube dorsal to trachea
Receives bolus from pharynx & carries it to stomach
Uses peristalsis (rhythmic, wavelike, involuntary muscular movement) to move food in a forward direction

17. 4. Stomach Enlarged part of alimentary canal
Receives food from esophagus
Rugae=folds of the mucous membrane lining of the stomach
Rugae flatten out and disappear as stomach fills with food & expands

19. 4. Stomach
Cardiac Sphincter-circular muscle between esophagus & stomach; closes after food enters stomach to prevent food from going back up into esophagus
Pyloric Sphincter-between stomach and sm intestine, keeps food in stomach until food is ready to enter sm intestine

21. 4. Stomach Food stays in stomach 2-4 hrs
While in the stomach, gastric juices convert food into a semifluid=chyme
Gastric juices are made by glands in the stomach and contain hydrochloric acid and enzymes

23. 4. Stomach
Hydrochloric acid-kills bacteria, helps iron absorption, & activates the enzyme pepsin
Gastric juice enzymes include lipase and pepsin
Lipase-starts the chemical breakdown of fats
Pepsin-starts protein digestion

24. 5. Small Intestine
Small intestine=coiled section of alimentary canal, about 20 ft. long and 1” in diameter
Chyme leaves stomach and enters sm intestine
Sm intestine is divided into 3 sections: duodenum, jejunum, ileum

26. 5. Small Intestine
Sm intestine produces intestinal juices that break down food
Digestion is completed in sm intestine
Products of digestion are absorbed into bloodstream for use by body cells
Walls of sm intestine are lined with villi
Villi=fingerlike projections containing capillaries & lacteals

28. 5. Small Intestine
Capillaries absorb the digested nutrients & carry them to the liver
Lacteals absorb digested fats and carry them to the thoracic duct
When food has completed its way through the sm intestine, only wastes, indigestible materials, & excess water is left

29. 5. Sm Intestine-Intestinal Juices
Maltase, sucrase, lactase=enzymes that break down sugars into simpler forms
Peptidases=enzymes that complete the digestion of proteins
Steapsin (lipase)=enzyme that aids in the digestion of fat

30. 5. Small Intestine-Duodenum
1st 9-10 inches of the sm intestine
Bile (from gallbladder and liver) and pancreatic juice enter duodenum through ducts or tubes

32. 5. Small Intestine-Jejunum
Next 8 ft.
Middle section of the sm intestine

33. 5. Small Intestine-Ileum
Final 12 ft.
Connects with lg intestine at cecum
Ileocecal Valve= circular muscle, separates ileum & cecum; prevents food from returning to ileum

36. 6. Large Intestine Final section of the alimentary canal
About 5 ft long, 2 inches in diameter

37. 6. Large Intestine Functions: Absorb water & any remaining nutrients
Store indigestible materials before they are eliminated from the body
Synthesis (formation) & absorption some B vitamins & vitamin K
Transport waste out of the alimentary canal

38. 6. Large Intestine Divided into a series of connected sections
1st section=cecum
Cecum connects to ileum of sm intestine and contains vermiform appendix (small projection)
2nd section=colon
Colon has 5 divisions

40. 6. Large Intestine Divisions of the colon:
Ascending colon=continues up on the R side of the body from the cecum to the lower part of the liver

41. 6. Large Intestine Divisions of the colon:
Transverse colon=extends across the abd, below the liver & stomach & above the sm intestine

42. 6. Large Intestine Divisions of the colon:
Descending colon=extends down the L side of the body, connects with sigmoid colon

43. 6. Large Intestine Divisions of the colon:
Sigmoid colon= S-shaped section that joins with the rectum

44. 6. Large Intestine Divisions of the colon:
Rectum=final 6-8 inches; storage area for indigestibles & wastes. It has a narrow canal (anal canal) which opens at a hole called the anus where fecal material (stool) is expelled. Stool is the final waste product of digestion
6. Large Intestine

46. Accessory Organs
Include:
Liver
Gallbladder
Pancreas

48. 1. Liver Largest gland in the body
Located in under diaphragm, in RUQ of abd
Secretes bile into sm intestine
Bile=enzyme that emulsifies (physically breaks down) fats & makes them water soluble

50. 1. Liver Stores sugar in the form of glycogen
Glycogen is converted to glucose & released into blood when additional sugar is needed
Stores iron & vitamins
Produces heparin (prevents clotting of blood)

51. 1. Liver
Produces blood proteins fibrinogen & prothrombin (aid in clotting)
Produces cholesterol
Detoxifies (renders harmless) substances like alcohol & pesticides
Destroys bacteria have been taken into the blood from the intestine

53. 2. Gallbladder Small, muscular sac located under the liver
Attached to liver by connective tissue
Receives, stores, & concentrates bile from liver
When bile is needed, gallbladder contracts & pushes bile through the cystic duct into the common duct which drains into the duodenum

55. 4. Pancreas Glandular organ located behind the stomach
Produces pancreatic juices which contain enzymes to digest food
Juices enter duodenum through the pancreatic duct

57. 4. Pancreas Pancreatic enzymes: Amylase (Amylopsin)=breaks down sugars
Trypsin & Chymotrypsin=breaks down proteins
Lipase (Steapsin)=breaks down fats
Pancreas also produces insulin which is secreted into the bloodstream
Insulin regulates the metabolism (burning) of carbohydrates to convert glucose (blood sugar) to energy